The present invention relates to a resin-molded semiconductor and to an apparatus for producing the same. More particularly, it relates to a resin-molded semiconductor which can be produced with an improved use efficiency of resin and to an apparatus provided with a mold for the resin-molded semiconductor.
Recently the multipot molding system has come into general use to rationalize the molding step for semiconductors. According to this system, one mold is provided with a plurality of pots and plungers and the molding resin is transferred into each cavity from each pot through a short runner. An advantage of this system over the conventional monopot molding system is that the molding resin can be used efficiently and the molding cycle can be reduced. On the other hand, this system compels one to use an extremely expensive molding resin incorporated with a large amount of high-purity filler in the case of semiconductors such as memory packages which require a high reliability. This makes it necessary to improve the use efficiency of resin to a great extent.
An example of the conventional multipot molding apparatus is disclosed in Japanese Patent Publication No. 35576/1982. It is constructed such that one mold has a plurality of pots and the molding resin is fed under pressure to them through the runners which are independent from one another. However, it is still unsatisfactory in the use efficiency of molding resin. In other word, there is a limit in improving the ratio of the amount of resin in the cavity to the amount of total resin including resin in pots and runners. This is because the cavities are disposed in parallel with each runner and the flow path in the mold is limited in layout.
Another example of the conventional apparatus is disclosed in Japanese Utility Model Publication No. 154074/1981. The mold in this utility model is constructed such that a plurality of lead frames are disposed at one side of and in parallel with the runner in the mold. In other words, a plurality of cavities are disposed in the direction perpendicular to the runner. This mold has one pot from which resin is filled through a long runner into a plurality of cavities disposed in parallel with and at a right angles to the runner. This arrangement gives rise to a large flow of resin in the runner, and this leads to an increased pressure loss due to flow resistance. If the sectional area of the runner is reduced to improve the use efficiency of resin, the flow resistance increases more, making it impossible to transfer the resin within a preset time. This leads to the occurrence of internal defects such as voids. For this reason, the runner has to have a certain sectional area and hence there is a limit in improving the use efficiency of resin.